A patient who has had an acute ischaemic stroke is to be treated with alteplase. Within what time frame must treatment be given after onset?

• A. Within 2 hours
• B. Within 3 hours
• C. Within 4.5 hours
• D. Within 6 hours

Answer: (C)

In acute ischemic stroke, restoring blood flow with intravenous alteplase works best when given as soon as possible, and the approved window is within four and a half hours from symptom onset in eligible patients. This four-and-a-half-hour limit comes from trials like ECASS III, which showed a net benefit in functional outcomes when alteplase is given up to that time, with careful patient selection. Waiting longer than four and a half hours increases the risk of bleeding in the brain and reduces the likelihood of a meaningful benefit, so treatment beyond this window is not routinely recommended. Earlier timeframes (such as within two or three hours) were important in earlier guidelines, but the recognized maximum window for IV thrombolysis has been extended to four and a half hours.